class Enlarge {
    constructor(el) {
        this.el = document.querySelector(el)
        this.imgObj = this.el.querySelector('.img')
        this.maskObj = this.el.querySelector('.mask')
        this.enlargeObj = this.el.querySelector('.enlarge')
        this.init()
    }
    init() {
        this.overOut()
        this.enlargeSetWH()
        this.maskMove()
    }
    enlargeSetBg(left, top) {
        let enlargeW = parseFloat(this.getStyle(this.enlargeObj, 'width'))
        let enlargeH = parseFloat(this.getStyle(this.enlargeObj, 'height'))
        let maskW = parseInt(this.getStyle(this.maskObj, 'width'))
        let maskH = parseInt(this.getStyle(this.maskObj, 'height'))
        let x = (enlargeW / maskW) * left
        let y = (enlargeH / maskH) * top
        this.enlargeObj.style.backgroundPosition = `-${x}px -${y}px`
    }

    maskMove() {
        this.imgObj.onmousemove = (evt) => {
            enlarge2
            let e = evt || window.event
            let left = e.pageX - this.imgObj.parentNode.offsetLeft - this.maskObj.offsetWidth / 2
            let top = e.pageY - this.imgObj.parentNode.offsetTop - this.maskObj.offsetHeight / 2
            if (left < 0) left = 0
            if (top < 0) top = 0
            let maxLeft = this.imgObj.offsetWidth - this.maskObj.offsetWidth
            let maxTop = this.imgObj.offsetHeight - this.maskObj.offsetHeight
            if (left > maxLeft) left = maxLeft
            if (top > maxTop) top = maxTop
            this.maskObj.style.left = left + 'px'
            this.maskObj.style.top = top + 'px'
            this.enlargeSetBg(left, top)
        }
    }

    getStyle(tagObj, attrName) {
        if (window.getComputedStyle) {
            return window.getComputedStyle(tagObj)[attrName]
        } else {
            return tagObj.currentStyle[attrNamea]
        }
    }
    enlargeSetWH() {
        let maskW = parseInt(this.getStyle(this.maskObj, 'width'))
        let maskH = parseInt(this.getStyle(this.maskObj, 'height'))
        let enlarge = this.getStyle(this.enlargeObj, 'background-size')
        let enlargeW = parseInt(enlarge.split(' ')[0])
        let enlargeH = parseInt(enlarge.split(' ')[1])
        let imgW = this.imgObj.clientWidth
        let imgH = this.imgObj.clientWidth
        this.enlargeObj.style.width = maskW * (enlargeW / imgW) + 'px'
        this.enlargeObj.style.height = maskH * (enlargeH / imgH) + 'px'
    }
    overOut() {
        this.imgObj.onmouseover = () => this.maskObj.style.display = this.enlargeObj.style.display = 'block'
        this.imgObj.onmouseout = () => this.maskObj.style.display = this.enlargeObj.style.display = 'none'
    }
}